Since the terrorist attack on the United States on Sep. 11, 2001, security issues have received greatly increased attention in the United States and elsewhere. Searches of personnel for weapons and explosives are routine for air travel and for access to many other events and facilities. Portal systems are regularly used to detect weapons and explosives. Operators with these systems preferably should be able to complete a scan in a few seconds. The most common prior art systems are metal detectors for personnel screening and x-ray systems for examining luggage.